Extra oral/panoramic dental imaging is nowadays a very common practise in a medical treatment of patients. Typical X-ray apparatus used for extra oral/panoramic dental imaging includes a rotative arm suspended at one end of a support column and an X-ray generating device and an X-ray detecting device (C-arm) oppositely fixed to respective ends of the rotative arm. The X-ray detecting device (C-arm) is typically a film-based device or CCD-based (Charged Coupled Device) device. The X-ray exposure is performed with rotation of the arm so that the movements of the rotative arm and thus also movements of the X-ray generating device and the X-ray detecting device are synchronized in such a way that an image of an area of desired shape, for example the patient's dental arch, is obtained on the film or CCD-device.
In panoramic X-ray imaging it is known, in order to obtain a sharp image of the dental arch, to allow the rotational axis of the support arm to move during the exposure in a predetermined manner linearly or non-linearly in such a way that this movement is dependent on the angular position of the support arm at each given time. The movement of the rotational axis may be linear, and parallel to the axis of symmetry of the dental arch, perpendicular to it, curved, or non-continuous between predetermined points.
In order to obtain a certain sharp panoramic image layer of an object to be determined it is very important to position the object accurately to the correct place in relation to the imaging apparatus. If another panoramic layer is desired as a sharp layer, either the imaging apparatus or the object to be determined must be shifted or repositioned. In practice the shifting and repositioning of the object is always cumbersome and time-consuming. Furthermore, the known X-ray photography apparatus do not always provide so extensive possibilities for positioning and use as are generally desired in order to obtain a precise image of some specific area or part of an area.